Home » Analysis: 2015 Mustang IRS! (engineering mule)

Analysis: 2015 Mustang IRS! (engineering mule)

by DrivingEnthusiast

Very exciting news for Ford fans (and true driving enthusiasts) this week, revealed by Car and Driver: http://www.caranddriver.com/news/2015-ford-mustang-spy-photos-news! A lucky spy photographer for KGP Photography found an engineering mule of the 2015 Mustang with an independent rear suspension underneath. And managed to get some fairly detailed pictures. The pictures tell us four things:

– The 2015 Mustang will finally enter the 21st century and shed ye olde ox-cart solid rear axle
– The 2015 Mustang is based on a revision of the current S197 platform, not an all-new design. Even with the Ford Evos Concept-like styling that will no doubt be its highlight, it’s simply an evolution of the current car. And it’s essentially the same width – possibly a couple of inches at wider at most.
– The independent rear suspension that was originally developed for the S197 for 2005 has been superseded by this all-new design.
– Given the update of the existing platform, the “S197+” chassis probably has another 6 years of use. More if the economy in 2020 is poor or if the market for this type of product declines. Or if the S197 platform remains an “orphan” – meaning it does not fit into “One Ford” planning.

And these also tell us that cavemen are no longer driving the future direction of this product. That is, a non-representative subset of owners, probably .0001%, who use the car to go only in a straight line. Lets hope that same kind of sample set doesn’t drive our Federal election this November!

So, unless another disaster happens inside Ford, we will finally have an independent rear suspension in the Mustang, 11 years after one was last offered. That’s progress, Ford style.

First let’s review some history, so that you can see the warning signs and get a heads-up in case it happens again. In 2004, Phil Martens (Group Vice President, Product Creation) canceled the IRS that had been developed in a fit of cost-cutting of various programs including the then-new 2005 Mustang. The IRS was axed, followed by the 7 liter engine, followed by the SVT Cobra (replaced by a dumbed-down iron-block solid-axle Mustang labeled “Shelby” – which could have been called anything but ended up as a licensing scheme from Shelby himself for a product that he didn’t have any engineering input into). Then Martens himself was “cancelled” and out the door from the company. Good riddance. And then Hau Thai-Tang (former Director, Advanced Product Creation and Special Vehicle Team:), who had given the press statements that an IRS would indeed be offered, backtracked and told us we didn’t need it anyway – labeling us all as “snobs”. In progression over the course of several months, he went from addressing the requirements of Ford customers (and customers who would be new to the brand) and promising they would be met, to outright insulting them:

  1. “Drag racers and Ford’s accountants will be pleased at the choice of a live axle out back. Among our customer groups that know and care what sort of rear suspension their car has, a large number of them want a solid rear axle; they’re primarily the core enthusiast drag racers, and they like the durability, reliability, and ease of modification with it, changing axle ratios, etc.,” says Thai-Tang. “There’s another group that wants the sophistication and cornering advantage of an IRS, and we’re going to offer it on the upcoming SVT Cobra. Unlike the last time, when we kind of shoehorned the IRS in [an older platform]; this time, we’ve designed the rear architecture to accommodate both right from the beginning.”
  2. “Ninety-two percent of (Mustang) Cobra customers wouldn’t have considered a Ford product”
  3. We’ll never appease those IRS snobs.”

And then, thankfully, Hau Thai-Tang was himself ”cancelled”, sent to South America to lead the development of a micro-SUV. Unfortunately, now he is back in the corporate HQ in Dearborn and will hopefully stay out of the way of the delivery of the IRS. In our opinion, after watching his progression of statements above, it would have been better for the Mustang if he had stayed in exile in South America. Hau Thai-Tang is a corporate apologist, and no friend of driving enthusiasts.

And let’s make one other point perfectly clear: the IRS suspension below has zero relationship to the Australian Falcon “Control Blade” IRS. That idea was dropped over 10 years ago. The Falcon’s Control Blade suspension was never seriously considered because it’s too flimsy, has poor geometry, and is not strong enough for the power that was planned for the 2005-up  Mustang. If Motor Trend had more thoroughly researched their article on this topic, the question would never have come up again.

Now let’s go to the real thing. The pictures published by Car and Driver are extremely interesting, note the copyrights and be sure to read the full article above. Here is our reaction to them.

This is likely the final production prototype of the IRS, but it is installed into a current 2013 model year car. This tells us that the rear track of the 2015 Mustang will be all-but identical, along with the rear frame rails and related hard points. Lots of details here of interest:

  • Fits neatly in the existing space. Unlike the S197 prototype (or the 99-04 SVT Cobra, which used very lightweight but strong hydro-formed steel tubing) this time a series of steel stampings are used for the structural subframe member. It appears to be a bolt-in. It’s going to be inexpensive to build, quick to install from the assembly line perspective, and unless the frame is changed further would also allow a solid axle to be used in some cases. Apparently we can’t relegate the caveman to the fringes of society.
  • Production cost has been addressed: instead of a multitude of expensive castings and forgings found in the S197 IRS prototype of 2005, this one is built mostly of welded steel stampings.
  • A new differential carrier, unrelated to any earlier carrier (such as the Explorer 8.8 used in the prior design). And, we would suspect from the shape that this is no longer the familiar 8.8″ – perhaps Ford farmed it out to ZF? Cooling fins on the rear cover (good, but too few), along with provisions for drain and fill that could be used for a cooler for track usage. In the rear it is mounted to the upper structural beam of the subframe with two large rubber/composite bushings.
  • Prototype exhaust, hacked together, and not in final form (look at the individual sections, some with mandrel bends – as well as the odd bends coming out of the resonator). As far as we can tell, it is a one-piece exhaust from the cats all the way back. This is unlikely for production; the rear section will probably be replaceable.

  • The lower arm is a nice aluminum casting, but it is not an a-arm. Instead, it goes from a single inboard point to a single point on the hub upright. On the front side is the toe-control link, which appears to be a steel stamping. Note the adjustable toe – and also the lack of camber adjustment on the lower aluminum arm. Hopefully one is provided on the upper arm.
  • A separate spring and shock is used, similar to the current Nissan FM platform rear suspension. Look at the spring “cup”. The upper mounting points on the frame for the shock and spring are probably identical to the current S197. That’s a critical point for putting both a solid axle and an IRS car down the same assembly line – IF that is what is indeed going to happen.
  • The sway bar end link is very much outboard, likely providing a 1-1 motion ratio. Very effective.
  • It’s difficult to tell what type of upper arm is used… stretching a bit we think we see a steel stamping but it is hard to tell.
  • A center resonator is used just before the differential.
  • This shot also shows some of the non-production fabrication of the exhaust system. In our opinion, the mounting should be reworked because enthusiasts will want to look under the car at the IRS and the two hanger brackets are in the way and look bad. The IRS is a point of technology and of pride – owners will want to show it off.

  • A closer view of the right left suspension. It’s not immediately clear how the suspension bolts into the car.
  • The dark black steel stamping to the upper right  appears to be there solely to mount the swaybar.
  • The parking brake appears to be cable-operated and external (part of the caliper – note the circular tension spring), instead of the better drum-in-rotor design which would allow a set of Brembo 2- or 4-piston calipers to be used. This is a change from the earlier S197 prototype and a disappointment. It’s possible that the caliper is the same iron single piston with integral parking brake that is used on the solid axle car. That’s a shame and a cost-cutting design. No telling if the rotors are solid or vented here… would be hard to believe that could be solid but it’s been done before on Mustangs.
  • We can also see a little more of the structure of the IRS subframe here… a structure crossing over in front of the carrier, and a longitudinal reinforcement between that and the toe-control mounting point.

What else do we know at this point?

  • Styling will change according to J Mays, getting away from the traditional mid-sixties styling and more to the modern. Look at the Evos as the guide here.
  • A new EcoBoost 2.3 liter 4-cylinder will be either the entry-level engine, or the first option. And don’t insult the original SVO by calling this an SVO. The SVO was the top of the line premium Mustang, a better car all around than the GT, and faster in any performance measure. Especially on the race track (and this author had back-to-back ownership of original GTs and SVOs to prove it on Watkins Glen).
  • The 3.7 V-6 and 5 liter V-8 were designed from the start for Direct Injection. Port was used at first to keep costs down.
  • The Mustang will be sold worldwide, particularly in Europe. With the far more sophisticated M3 costing far more dollars going forward, the Mustang could be a viable alternative to buyers who could settle for some significant loss of refinement in return for a familiar size and performance return.

What don’t we know?

  • Whether the MT82 transmission disaster will be fixed, permanently (rather than by band-aid). The transmission design is inherently extremely weak, and has too little fluid for effective cooling.
  • Whether the 3.7 and 5 liter engines will get Direct Injection in the first year… or as in the SN95 and S197 the “improved” engines will come to market 2 years or more after the initial new platform does. Leaving the initial owners with obsoleted cars and half of their car payments left. In our humble opinion, they had better have it: D.I. provides nothing but benefit (mileage, emissions, drivability, tune-ability, performance). Perhaps Ford will introduce further improvements such as variable valve lift technology 2-3 years into the cycle.
  • How much the 2005 Mustang will weigh. Ford has a program to take literally several hundred pounds out of their existing cars over the course of this decade… it’s hard to see how this can be done on the existing or updated S197 platform. A couple of inches bobbed off the back of the car (about 5, judging from the pictures) and a lot more high-strength steel isn’t going to do it. We’d bet on a hundred or so pounds shed… and any major loss to wait for an all-new platform some other decade. Plan for the full-tilt models to push 3800 pounds.
  • What this suspension and revised S197 platform could mean to the future of the Ford Falcon…. perhaps as much as parts sharing and (stretching even further) Federalization of a replacement Falcon on the 2015 Mustang platform (Ford has commitments with the Australian Government to build a locally-sourced Falcon in Australia until 2016). And what this might mean to any future rear-wheel drive Lincoln. Now we’re really dreaming… even with Ford rolling in record profits, this seems too unlikely to be possible given the history of the company.
  • How the 2015 Mustang will stack up against the 2016 Camaro (built on the new and even more-sophisticated Alpha platform shared with the Cadillac ATS). It doesn’t look good.

Now comes the difficult part: the long wait for the production car. Before then we will certainly see additional mules and eventually full prototypes. Perhaps at the NAIAS in 2013 we might even see a concept… however given the sales failings of the current Mustang anything that might put potential buyers on hold would further hurt Ford. It’s a sure bet that we’ll see the production car at NAIAS 2014 and an April 2014 launch.

Kudos to Car and Driver yet again! We very clearly remember the day we returned from a disappointing test drive of a ’78 Mustang II Cobra II to find an issue of Car and Driver in our mail box with the first spy pictures of the upcoming new ’79 Mustang… and again many years later as we were wondering what to do with our ’91 Mustang when an issue arrived with a cover photo of a clay model of the upcoming ’94 Mustang.  At both those points in time we were never again going to buy another Mustang… and an early view of a much better future eventually led us to do so yet again. History may repeat itself here again.

Read more 2015 Mustang news on DrivingEnthusiast.net:

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